Chev 350 fuel consumption

[Gordon]

Saw Matte's post this morning re gas setups and didn't want to hijack that posting, so thought I would start a new one aimed at those out there who are running the Chev 350 conversion. I'm keen to hear what others are getting fuel consumption wise as I'm not too happy with what my van is returning at the moment. I average about 22.5 litres per 100km in town if I hoon and around 18.5 litres per 100km on the open road averaging around 100 kilometers per hour. This on a brand new factory GM motor running a Quickfuel 580 square bore 4 barrel carbie. The carbie was professionally tuned on a rolling road with the aid of an oxygen analyser. My box is a TH350 and my diff is a 3.0 to 1 ratio.

[taggraphx]

Seems not to bad in consumption, we just bought a 350 chev suburban, 3.2 ton of truck and that gets 16-18lt on the open road, not sure around town, I would have thought your van would get a bit better due to less weight, ours sits at 1700rpm at 100kph
 

[Sundownernz]

Hi Gordon,

Not sure what mine runs around town as all my fuel checks have been done on trips but I'm usually getting 16 mpg (old school) say 17.5 ltrs/100km. Mines a LWB running a 310HP 350, 350 turbo trans, 600 vac sec Holley and a 3.0 9"diff with 275 x 50 x 15 rubber on the rear. At 100 kph its running around 2600 rpm. Van probably weighs in at around 2.5 - 3 tonne. The figure doesn't seem to change even when towing our pop top camper which would add another 750kgs.

Hope this helps mate.
 

[Gordon]

Thanks for the info gents. Garry, I'm assuming your carbie is a spread bore version rather than square bore ie you have smaller venturies on your primaries. I thought that I wasn't doing to bad until Stu and I went on the same run down to Hamilton. Stu is running a Ford 302 behind a C4 transmission in his van, but with a 3.51 diff ratio which I thought would kill his consumption. He ended up returning 13.5 litres per 100 km compared to my 18.5. Granted his engine has a smaller cubic capacity, but the biggest difference is that he is running a Holley 350CFM two barrel carb. I'd be happy to sacrifice some grunt for better fuel consumption, but have read some conflicting reports about 2 barrel versus 4 barrel on some of the V8 forums.

[BusyKiwi]

I was going to suggest change your diff gears to 3.3:1 or 3.5:1 but you haven't said much about your rev range

A 4 barrel running on the primaries is cheaper to run than a 2 barrel, when you open up the secondaries it drinks more than the 2 barrel. I've always gone to 4 barrels for better fuel consumption.

Have you got an upgraded cam in your engine? for horse power you need cam, headers and carb combination
You also have to remember the bedford is aerodynamically challenged

[Gordon]

Busy, I don't currently run a rev counter so I'm not sure what revs I'm doing. I'm busy modifying a spare standard Bedford instrument cluster that will have a rev counter in place of the existing temp gauge, but I'll cover that modification in a future post. I will hook up the rev counter temporarily and will let you know what I'm getting.

My motor is running a factory standard cam and standard cast iron heads. I am runnign block hugger extractors and a two into one 2.5 inch exhaust system.

Stu has just changed his diff ratio from 3.5 to 3.0 and was going to monitor his fuel consumption this week to see what difference it has made to his van.

[Sundownernz]

Yeah mines a spreadbore, 1860 I think the model # is. Runs most of the time on the secondaries and still pulls well on full throttle when needed even with a 3.0 diff ratio. Has run upper 15's on the 1/4 mile but that was a while back when the motor was a bit fresher.

Keep us posted on the results from Stus trial with the ratio change. Be interested in the results.

Cheers,
Garry.

[Gordon]

Stu's just filled up and used 29 liters doing 210 kilometers. He reckons that was a 50/50 mixture of town and open road driving, so he will recheck on pure open road driving. 

[bed767]

I run a 308 holden with a tubo 700 with lockup on gas,thru a 3.08 one tonner diff,275/60 x15 on rear. Around town 20/100 on highway 16-17/100. Electric fans and water pump for less drag.

[Dano]

interesting post lads, my mild healthy  327, 5 spd used to get around 360km per 60ltrs on an open run, averaging 2150 - 2200 rpm, diff was 3 -1.  265 /50/ 14"    ( was not trying to save fuel either- I LOVE the roar especially through side pipes)

the lwb ......  tired 350, th350, 350 holley does alright, all around town re- kms ? not sure as the speedo has gone on holidays + it'd be 50 /50 throttle wise. I have just got a new special built 350 holley from the  "holley specialist" .... here in perth. he reckoned this would be the better option to the 650  spreadbore or 600 vac- as there is no real advantage for a std engine (no cam etc)

I always try to get as much fresh air in and out as I believe to with all engines, just simply make them breath .... extractors, good air cleaners, good spark, and good exhaust are as we know the basics.when time permits I would like to do the cold air intake pod thing, with some sort of scoop....again when and while I'm doing nothing...lol
I'll do some figures next break with a gps and see what evolves...
dano